Draw tube drive mechanism, spindle unit, and machine tool

Abstract

A draw tube drive mechanism includes a draw tube movable along a first axis of a rotation shaft, a moving member movable substantially perpendicularly to the first axis, a first link rotatably connected to the moving member via a first pin, a third link rotatably connected to the first link via a third pin to receive a force from the moving member and transmit the force to the draw tube, and a second link rotatably connected to the first link via a second pin and rotatably connected to the support via the fourth pin. The second pin is provided between the first and third pins. The first to third pins are arranged substantially on a straight line. Each of a distance between the first and second pins and a distance between the second and third pins is substantially equal to a distance between the second and fourth pins.

What is claimed is: 
     
         1 . A draw tube drive mechanism comprising:
 a draw tube movable along a first axis relative to a support which supports a rotation shaft rotatably about the first axis;   a driver configured to move a moving member in a moving direction substantially perpendicular to the first axis;   a first link connected to the moving member via a first pin rotatable around the first pin;   a third link connected to the first link via a third pin rotatable around the third pin and configured to receive a force from the moving member via the first link and to transmit the force to the draw tube;   a second link connected to the first link via a second pin rotatable around the second pin and connected to the support via the fourth pin rotatable around the fourth pin, the second pin being provided between the first pin and the third pin;   each of the first pin, the second pin, the third pin, and the fourth pin extending along a pin direction substantially perpendicular to both of the first axis and the moving direction;   the first pin, the second pin, and the third pin being arranged substantially on a straight line when viewed from a direction along the pin direction; and   each of a distance between the first pin and the second pin and a distance between the second pin and the third pin being substantially equal to a distance between the second pin and the fourth pin.   
     
     
         2 . The draw tube drive mechanism according to  claim 1 ,
 wherein the third link comprises
 a first portion connected to the first link via the third pin, 
 a bearing, and 
 a second portion supported by the first portion via the bearing provided between the first portion and the second portion, the second portion being rotatable about the first axis with the rotation shaft, and 
   wherein the draw tube is configured to rotate about the first axis with the rotation shaft and to be movable along the first axis relative to the rotation shaft.   
     
     
         3 . The draw tube drive mechanism according to  claim 2 , further comprising:
 a toggle comprising:
 a fulcrum about which the toggle is configured to pivot; 
 a pressed portion configured to be pressed by the second portion so that the toggle pivots about the fulcrum; and 
 a load point configured to press the draw tube along the first axis in a first direction and a fourth direction opposite of the first direction, upon the pressed portion being pressed. 
   
     
     
         4 . The draw tube drive mechanism according to  claim 1 ,
 wherein the first link comprises
 a left-side first link arranged on a left side with respect to the first axis, and 
 a right-side first link arranged on a right side with respect to the first axis, and 
   wherein the left-side first link and the right-side first link are coupled together via the third link.   
     
     
         5 . The draw tube drive mechanism according to  claim 4 ,
 wherein the third link comprises
 a left-side connecting portion connected to the left-side first link, 
 a right-side connecting portion connected to the right-side first link, and 
 a center portion having a through hole and disposed between the left-side connecting portion and the right-side connecting portion to connect the left-side connecting portion and the right-side connecting portion, the draw tube being provided to pass through the through hole. 
   
     
     
         6 . The draw tube drive mechanism according to  claim 1 ,
 wherein the driver is disposed at a higher position than the draw tube in a vertical direction, and   wherein the moving direction is substantially parallel to the vertical direction.   
     
     
         7 . The draw tube drive mechanism according to  claim 1 , further comprising:
 an operation lever configured to move the moving member in the moving direction, wherein the operation lever is attachable to and detachable from both the moving member and the support.   
     
     
         8 . A spindle unit comprising:
 a rotation shaft configured to hold a holding target;   a support supporting the rotation shaft rotatably about a first axis;   a rotary driver configured to rotate the rotation shaft about the first axis;   a draw tube movable in the first axis relative to the support;   a driver configured to move a moving member in a moving direction substantially perpendicular to the first axis;   a first link connected to the moving member via a first pin rotatable around the first pin;   a third link connected to the first link via a third pin rotatable around the third pin and configured to receive a force from the moving member via the first link and to transmit the force to the draw tube;   a second link connected to the first link via a second pin rotatable around the second pin and connected to the support via the fourth pin rotatable around the fourth pin, the second pin being provided between the first pin and the third pin;   each of the first pin, the second pin, the third pin, and the fourth pin extending along a pin direction substantially perpendicular to both of the first axis and the moving direction;   the first pin, the second pin, and the third pin being arranged substantially on a straight line when viewed from a direction along the pin direction; and   each of a distance between the first pin and the second pin and a distance between the second pin and the third pin being substantially equal to a distance between the second pin and the fourth pin.   
     
     
         9 . The spindle unit according to  claim 8 ,
 wherein the rotation shaft comprises
 a shaft, and 
 a holding member disposed inside the shaft and configured to hold the holding target, and 
   wherein the holding member converts a pressing force received from the draw tube into a holding force for holding the holding target.   
     
     
         10 . The spindle unit according to  claim 9 ,
 wherein the holding member includes one of a collet chuck and a hydraulic chuck.   
     
     
         11 . The spindle unit according to  claim 9 ,
 wherein the driver is entirely disposed between a first plane and a second plane, the first plane being defined as a vertical plane passing one end in the pin direction of the support and parallel to the first axis, and the second plane being defined as a vertical plane passing one end in a sixth direction, defined as being opposite of the pin direction, of the support and parallel to the first axis.   
     
     
         12 . A machine tool comprising:
 a machining head configured to hold a tool;   a machining head driver configured to move the machining head; and   a workpiece holding device comprising:
 a rotation shaft configured to hold a workpiece; 
 a support supporting the rotation shaft rotatably about a first axis; 
 a rotary driver configured to rotate the rotation shaft about the first axis; 
 a draw tube movable along the first axis relative to the support; 
 a driver configured to move a moving member in a moving direction substantially perpendicular to the first axis; 
 a first link connected to the moving member via a first pin rotatable around the first pin; 
 a third link connected to the first link via a third pin rotatable around the third pin and configured to receive a force from the moving member via the first link and to transmit the force to the draw tube; 
 a second link connected to the first link via a second pin rotatable around the second pin and connected to the support via the fourth pin rotatable around the fourth pin, the second pin being provided between the first pin and the third pin; 
 each of the first pin, the second pin, the third pin, and the fourth pin extending along a pin direction substantially perpendicular to both of the first axis and the moving direction; 
 the first pin, the second pin, and the third pin being arranged substantially on a straight line when viewed from a direction along the pin direction; and 
 each of a distance between the first pin and the second pin and a distance between the second pin and the third pin being substantially equal to a distance between the second pin and the fourth pin. 
   
     
     
         13 . The machine tool according to  claim 12 , further comprising:
 a support moving device configured to move the support;   a base supporting the support; and   a cover provided below the third link in a vertical direction and configured to extend and contract as the support moves,   wherein the driver is arranged above the third link in the vertical direction.